Composition based on 1,3,3,3-tetrafluoropropene

ABSTRACT

The subject of the present application is a composition comprising a lubricant based on polyol esters (POEs) or PVE and a refrigerant F comprising from 1 to 99% by weight of trans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze) and from 1 to 99% by weight of 1,1,1,3-tetrafluoroethane. The subject of the present application is also the use of said composition in refrigeration, air conditioning and heat pumps.

The present application claims priority from French application SerialNumber FR 10.57483 filed Sep. 20. 2010.

BACKGROUND OF THE INVENTION

The present invention relates to a composition containingtrans-1,3,3,3-tetrafluoropropene and 1,1,1,3-tetrafluoroethane and atleast one lubricant, capable of being used in refrigeration,air-conditioning and heat pumps.

The problems presented by substances which deplete the atmospheric ozonelayer were dealt with at Montreal, where the protocol was signedimposing a reduction in the production and use of chlorofluorocarbons(CFCs). This protocol has been the subject of amendments which haverequired the abandoning of CFCs and have extended the regulations toother products, including hydrochlorofluorocarbons (HCFCs).

The refrigeration and air-conditioning industry has invested a greatdeal in the replacement of these refrigerants and it is because of thisthat hydrofluorocarbons (HFCs) have been marketed.

In the motor vehicle industry, the air-conditioning systems of vehiclessold in many countries have been changed from a chlorofluorocarbon(CFC-12) refrigerant to a hydrofluorocarbon (1,1,1,2-tetrafluoroethane:HFC-134a) refrigerant, which is less harmful to the ozone layer.However, from the viewpoint of the objectives set by the Kyoto protocol,HFC-134a (GWP=1430) is considered to have a high heating power. Thecontribution of a refrigerant to the greenhouse effect is quantified bya criterion, the GWP (Global Warming Potential), which summarizes theheating power by taking a reference value of 1 for carbon dioxide.

Hydrofluoroolefins (HFOs) have a low heating power and thus meet theobjectives set by the Kyoto protocol. Document JP 4-110388 discloseshydrofluoropropenes as heat-transfer agents.

In the industrial sector, the refrigerating machines most commonly usedare based on cooling by evaporation of a liquid refrigerant. Aftervaporization, the refrigerant is compressed and then cooled in order toreturn to the liquid state and thus continue the cycle.

The refrigeration compressors used are of the reciprocating, scroll,centrifugal or screw type. In general, internal lubrication of thecompressors is essential in order to reduce wear and heating of themoving members, complete their leaktightness and protect them againstcorrosion.

In addition to good heat-transfer agent properties, in order for arefrigerant to be commercially accepted, it must in particular exhibitthermal stability and compatibility with the lubricants. Specifically,it is highly desirable for the refrigerant to be compatible with thelubricant used in the compressor, present in the majority ofrefrigeration systems. This combination of refrigerant and lubricant isimportant for the implementation and the efficiency of the refrigerationsystem; in particular, the lubricant should be sufficiently soluble ormiscible in the refrigerant over the entire operating temperature range.

Thus, polyalkylene glycols (PAGs) have been developed as lubricants ofHFC-134a in motor vehicle air conditioning. Tests for miscibility of1,1,3,3,3-pentafluoropropene and 1,3,3,3-tetrafluoropropene withlubricants have been described in Example 2 of document WO 2004/037913.Compatibility tests have also been described in Example 3, withpolyalkylene glycol. However, these tests do not specify the nature ofthe 1,3,3,3-tetrafluoropropene isomer.

Moreover, document WO 2005/108522 discloses an azeotropic composition oftrans-1,3,3,3-tetrafluoropropene and 1,1,1,3-tetrafluoroethane.

Just recently, 2,3,3,3-tetrafluoropropene was chosen as a refrigerantfor replacing HFC-134a in motor vehicle air conditioning.

The applicant has now developed a refrigerant and lubricant pairingwhich can be used in refrigeration, air conditioning and heat pumps.

DETAILED DESCRIPTION OF THE INVENTION

A subject of the present application is therefore a compositioncomprising at least one lubricant based on polyol esters (POEs) or onpolyvinyl ether (PVE) and a refrigerant F comprising from 1 to 99% byweight of trans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze) and from 1to 99% by weight of 1,1,1,3-tetrafluoroethane.

Preferably, the composition according to the present invention comprisesat least one lubricant based on polyol esters (POEs) or on polyvinylether (PVE) and a refrigerant F comprising from 5 to 95% by weight oftrans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze) and from 5 to 95% byweight of 1,1,1,3-tetrafluoroethane.

The composition which is particularly preferred comprises at least onelubricant based on polyol esters (POEs) or on polyvinyl ether (PVE) anda refrigerant F comprising from 30 to 91% by weight oftrans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze) and from 9 to 70% byweight of 1,1,1,3-tetrafluoroethane. The refrigerant F may also compriseother hydrofluorocarbons. The fluid F has the advantage of being moreeffective than trans-HFO-1234ze and, in addition, the stability of therefrigerant in the presence of POE or PVE is greater compared with thatof trans-HFO-1234ze in the presence of PAG.

Polyol esters are obtained by reaction of a polyol (an alcoholcontaining at least 2 hydroxyl groups —OH) with a monofunctional orplurifunctional carboxylic acid or with a mixture of monofunctionalcarboxylic acids. The water formed during this reaction is eliminated inorder to prevent the reverse reaction (i.e. hydrolysis).

According to the present invention, the preferred polyols are thosewhich have a neopentyl backbone, such as neopentyl glycol,trimethylolpropane, pentaerythritol and dipentaerythritol;pentaerythritol is the preferred polyol. The carboxylic acids maycontain from 2 to 15 carbon atoms, it being possible for the carbonbackbone to be linear or branched. Mention may in particular be made ofn-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid,2-ethylhexanoic acid, 2,2-dimethylpentanoic acid,3,5,5-trimethylhexanoic acid, adipic acid and succinic acid, andmixtures thereof.

Some alcohol functions are not esterified, however their proportionremains low. Thus, the POEs can comprise between 0 and 5 relative mol %of CH₂—OH units relative to the —CH₂—O—(C═O)— units.

The preferred POE lubricants are those which have a viscosity of from 1to 1000 centiStokes (cSt) at 40° C., preferably from 10 to 200 cSt, andadvantageously from 30 to 80 cSt.

The polyvinyl ether (PVE) oils are preferably copolymers of thefollowing 2 units:

The properties of the oil (viscosity, solubility of the refrigerant andmiscibility with the refrigerant in particular) can be adjusted byvarying the m/n ratio and the sum m+n. The preferred PVE oils are thosewhich have 50 to 95% by weight of units 1.

According to one preferred embodiment of the invention, the lubricantrepresents between 10 and 50%, inclusive, by weight of the composition.

The refrigerant F may also comprise additives such as odorous compounds.

A subject of the present invention is also the use of the abovementionedcomposition in refrigeration, in particular domestic or commercialrefrigeration, cold rooms, the food industry, the processing industry,refrigerated transport (trucks, boats); air conditioning, in particulardomestic, commercial or industrial air conditioning, where theappliances used are chillers or direct expansion appliances; and heatpumps, in particular medium- and high-temperature heat pumps.

By virtue of their low glide temperature, the compositions according tothe present invention can be used both in equipment with dry-expansionevaporators and in equipment with evaporators operating in a floodedsystem.

Experimental Section

The thermal stability trials are carried out according to standardASHRAE 97-2007: “sealed glass tube method to test the chemical stabilityof materials for use within refrigerant systems”.

The test conditions are as follows:

weight of refrigerant: 2.2 g

weight of lubricant: 5 g

temperature: 200° C.

duration: 14 days

The lubricant is introduced into a 42.2 ml glass tube. The tube is thenevacuated under vacuum and then the refrigerant F is added thereto. Thetube is then welded in order to close it and placed in an oven at 200°C. for 14 days.

At the end of the test, various analyses are carried out:

-   -   the gas phase is recovered in order to be analysed by gas        chromatography: the main impurities were identified by GC/MS        (gas chromatography coupled with mass spectrometry). The        impurities coming from the refrigerant F and those coming from        the lubricant can thus be combined;    -   the lubricant is analysed: colour (by spectrocolorimetry,        Labomat DR Lange LICO220 Model MLG131), water content (by Karl        Fischer coulometry, Mettler DL37) and acid number (by        quantitative determination with 0.01N methanolic potassium        hydroxide).

Three commercial lubricants were tested: the PAG ND8 oil, the POEZe-GLES RB68 oil and the PVE FVC 68D oil.

PVE FVC PAG ND8 POE Ze-GLES RB68 68D Trans-HFO- Trans-HFO- Trans-HFO-Refrigerant HFC-134a 1234ze HFC-134a 1234ze 1234ze By-products in thegas phase: from the 100 ppm 4000 ppm + 100 ppm 500 ppm + 3% +refrigerant 6000 ppm 1500 ppm 1800 ppm (HFO-1234yf) (HFO-1234yf)(HFO-1234yf) from the 1.5% 2% 500 ppm 800 ppm 2% lubricant Analysis ofthe lubricant: colour 400 Hazen 17 Gardner 300 Hazen 300 Hazen 6 Gardnerwater content 1200 ppm 1100 ppm 160 ppm 500 ppm 500 ppm acid number 1.5mg >10 mg 0.3 mg 0.6 mg 1.1 mg KOH/g KOH/g KOH/g KOH/g KOH/g It is notedthat trans-HFO-1234ze in the presence of POE or PVE improves thestability of the lubricant. In addition, in the presence of POE, thestability of the refrigerant is also improved.

Applications

Thermodynamic performance of the systems using the mixtures in question

Calculation Tools

The RK-Soave equation is used for the calculation of the densities,enthalpies, entropies and the liquid-vapour equilibrium data of themixtures. The use of this equation requires knowledge of the propertiesof the pure substances used in the mixtures in question and also thecoefficients of interaction for each binary combination.

The Data Necessary for Each Pure Substance are:

boiling point, critical pressure and temperature, curve of pressure as afunction of temperature starting from the boiling point to the criticalpoint, saturated liquid and saturated vapour densities as a function oftemperature.

The data on HFCs are published in the ASHRAE Handbook 2005 chapter 20and are also available under Refrop (software developed by NIST forcalculating the properties of refrigerants).

The HFO temperature-pressure curve data are measured by the staticmethod. The critical pressure and temperature are measured using a C80calorimeter sold by Setaram. The densities, at saturation as a functionof temperature, are measured by means of the vibrating tube densimetertechnology developed by the laboratories of the école des Mines de Paris[French Engineering School].

Coefficient of Binary Interaction:

The RK-Soave equation uses coefficients of binary interaction torepresent the behaviour of products in mixtures. The coefficients arecalculated according to experimental liquid-vapour equilibrium data.

The technique used for the liquid-vapour equilibrium measurements is thestatic analytical cell method. The equilibrium cell comprises a sapphiretube and is equipped with two Rolsitm electromagnetic samplers. It isimmersed in a cryothermostat bath (Huber HS40). Magnetic stirring drivenby a magnetic field rotating at a variable speed is used to acceleratethe reaching of the equilibria. The sample analysis is carried out bygas chromatography (HP5890 series II) using a katharometer (TCD).

HFC-134a/Trans-HFO-1234ze

The liquid-vapour equilibrium measurements on theHFC-134a/trans-HFO-1234ze binary combination are carried out for thefollowing isotherm. 20° C.

Compression System

Consider a compression system equipped with an evaporator, a condenser,a liquid-vapour exchanger (internal exchanger), a screw compressor and apressure regulator.

The system operates with 15° C. of overheat and an internal exchangerbetween the outlets of the condenser and of the evaporator.

The isentropic efficiency of the compressors depends on the compressionratio. This efficiency is calculated according to the followingequation:

$\begin{matrix}{\eta_{isen} = {a - {b\left( {\tau - c} \right)}^{2} - \frac{d}{\tau - e}}} & (1)\end{matrix}$

For a screw compressor, the constants a, b, c, d and e of the isentropicefficiency equation (1) are calculated according to the standard datapublished in the “Handbook of air conditioning and refrigeration, page11.52”.

The coefficient of performance (COP) is defined as being the usefulpower supplied by the system over the power provided or consumed by thesystem.

The Lorenz coefficient of performance (COPLorenz) is a referencecoefficient of performance. It depends on temperatures and is used tocompare the COPs of the various refrigerants.

The Lorenz coefficient of performance is defined as follows: (thetemperatures T are in K)

T _(average) ^(condensor) =T _(inlet) ^(condensor) −T _(outlet)^(condensor)   (2)

T _(average) ^(evaporator) =T _(outlet) ^(evaporator) −T _(inlet)^(evaporator)   (3)

The Lorenz COP in the Case of Conditioned Air and Refrigeration:

$\begin{matrix}{{COPlorenz} = \frac{T_{average}^{evaporator}}{T_{average}^{condensor} - T_{average}^{evaporator}}} & (4)\end{matrix}$

The Lorenz COP in the Case of Heating:

$\begin{matrix}{{COPlorenz} = \frac{T_{average}^{condensor}}{T_{average}^{condensor} - T_{average}^{evaporator}}} & (5)\end{matrix}$

For each composition, the coefficient of performance of the Lorenz cycleis calculated as a function of the corresponding temperatures.

The %COP/COPLorenz is the ratio of the COP of the system relative to theCOP of the corresponding Lorenz cycle.

Results in Cooling Mode

In cooling mode, the compression system operates between an evaporationtemperature of −5° C. and a condensation temperature of 50° C.

The values of the constituents (HFC-134a, trans-HFO-1234ze) for eachcomposition are given as percentage by weight.

Cooling mode Temp T evap Temp comp condensation T pressure Evap CondRatio Comp % % COP/ inlet (° C.) outlet (° C.) (° C.) regulator P (bar)P (bar) (w/w) Glide efficiency CAP COPLorenz HFO- −5 73 50 42 1.8 10.05.6 0.00 74.8 100 54 1234ze HFO- HFC- 1234ze 134a  5 95 −5 81 50 42 2.413.1 5.4 0.03 75.9 136 56 10 90 −5 81 50 42 2.4 13.0 5.4 0.07 75.8 13555 20 80 −5 80 50 42 2.3 12.8 5.5 0.16 75.6 131 55 30 70 −5 79 50 42 2.312.6 5.5 0.26 75.3 128 55 40 60 −5 79 50 42 2.2 12.3 5.6 0.34 75.1 12454 50 50 −5 78 50 42 2.1 12.0 5.6 0.40 74.9 120 54 60 40 −5 78 50 42 2.111.7 5.7 0.44 74.7 116 54 70 30 −5 77 50 42 2.0 11.3 5.7 0.43 74.6 11254 80 20 −5 76 50 42 1.9 10.9 5.7 0.37 74.5 108 54 90 10 −5 75 50 42 1.810.5 5.7 0.24 74.6 104 54 95  5 −5 74 50 42 1.8 10.3 5.7 0.14 74.6 10254

Results in Heating Mode

In heating mode, the compression system operates between an evaporationtemperature of −5° C. and a condensation temperature of 50° C.

The values of the constituents (HFC-134a, trans-HFO-1234ze) for eachcomposition are given as percentage by weight.

Heating mode Temp T evap Temp comp condensation T pressure Evap CondRatio Comp % % COP/ inlet (° C.) outlet (° C.) (° C.) regulator P (bar)P (bar) (w/w) Glide efficiency CAP COPLorenz HFO- −5 73 50 42 1.8 10.05.6 0.00 74.8 100 62 1234ze HFO- HFC- 1234ze 134a  5 95 −5 81 50 42 2.413.1 5.4 0.03 75.9 136 63 10 90 −5 81 50 42 2.4 13.0 5.4 0.07 75.8 13563 20 80 −5 80 50 42 2.3 12.8 5.5 0.16 75.6 131 63 30 70 −5 79 50 42 2.312.6 5.5 0.26 75.3 128 63 40 60 −5 79 50 42 2.2 12.3 5.6 0.34 75.1 12462 50 50 −5 78 50 42 2.1 12.0 5.6 0.40 74.9 120 62 60 40 −5 78 50 42 2.111.7 5.7 0.44 74.7 116 62 70 30 −5 77 50 42 2.0 11.3 5.7 0.43 74.6 11262 80 20 −5 76 50 42 1.9 10.9 5.7 0.37 74.5 108 62 90 10 −5 75 50 42 1.810.5 5.7 0.24 74.6 104 62 95  5 −5 74 50 42 1.8 10.3 5.7 0.14 74.6 10262

1. Composition comprising at least one lubricant comprising polyolesters or polyvinyl ether and a refrigerant F comprising from 1 to 99%by weight of trans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze) andfrom 1 to 99% by weight of 1,1,1,3-tetrafluoroethane.
 2. Compositionaccording to claim 1, characterized in that the refrigerant F comprisesfrom 5 to 95% by weight of trans-1,3,3,3-tetrafluoropropene(trans-HFO-1234ze) and from 5 to 95% by weight of1,1,1,3-tetrafluoroethane.
 3. Composition according to claim 1,characterized in that the refrigerant F comprises from 30 to 91% byweight of trans-1,3,3,3-tetrafluoropropene (trans-HFO-1234ze) and from 9to 70% by weight of 1,1,1,3-tetrafluoroethane.
 4. Composition accordingto claim 1, characterized in that the polyol esters are obtained frompolyols having a neopentyl backbone.
 5. Composition according to claim4, characterized in that the polyol having a neopentyl backbone isselected from the group consisting of neopentyl glycol,trimethylolpropane, pentaerythritol and dipentaerythritol. 6.Composition according to claim 1, characterized in that the polyolesters are obtained from a linear or branched carboxylic acid containingfrom 2 to 15 carbon atoms.
 7. Composition according to claim 1,characterized in that the polyol esters represent between 10 and 50% byweight of the composition.